On the surface, it’s a brilliant prank: he found a way to create a…

The Ultimate Retaliation: Pranking My Roommate With Targeted Facebook Ads

On the surface, it's a brilliant prank: he found a way to create a custom targeted audience of just one person, about whom he knew more than Facebook's ad system did. But it shows the potential for online harassment, especially since it ties in with our fears about online privacy.